WORCESTER — First came the harrowing slide on unseen ice. Then the crunch of sheet metal. Then the jarring impact from behind as the next car plowed into the pack.

Now cue the paperwork and potentially higher car insurance premiums for years to come.

The good news for dozens of drivers involved in last Sunday morning's pileup on an icy stretch of Interstate 290 is that state police say they won't issue any traffic citations as a result of the mega-crash.

But that doesn't mean some insurance companies won't try to hit involved drivers with surcharges that could add thousands of dollars to their annual insurance premiums for the next six years.

"If you had collision insurance, your insurance company is going to pay for the damage subject to your deductible. Who's at fault, though, that's another issue," said Francis P. Shea, a principal of The Sullivan Group, an insurance agency based in Worcester. "You've got 65-odd cars and vehicles all piled up. Who started it all? Is it the guy in front? The rear? I don't know how they're going to sort all that out."

Two people suffered serious injuries and 35 people suffered minor injuries in the crashes along a 1,500-foot-long swath of the highway, Massachusetts State Police said. Included in the 65-vehicle pileup were two tractor-trailer units and two six-wheel commercial vehicles.

The prospect of investigating and writing some five dozen separate accident reports prompted state police to take the rare step of preparing a single accident report, said spokeswoman Trooper Nicole Morrell. The report has yet to be released.

"There will be no charges, criminal or civil, from state police," Trooper Morrell said. "The cause of the crash will be listed as 'weather and road conditions,' and we're assuming insurance companies will abide by that for surcharge reasons."

That remains to be seen.

But if the assumption proves to be in error, drivers would have a good shot at winning a surcharge appeal before the state Division of Insurance's Board of Appeal, industry observers said.

The Sullivan Group's Mr. Shea said auto insurance companies in Massachusetts typically surcharge customers as a result of any crash in which the company has to pay out a claim of $500 or more. If another driver had been at fault, that person's insurance company would have to pay for the damage, he noted.

The whole idea of a surcharge is that if you've had an accident, you represent a higher risk and therefore you should be charged more, explained Frank O'Brien of the Property Casualty Insurer Association of America, a trade group that represents a number of automobile insurance companies that do business in Massachusetts.

But figuring out who is the risk and who just got hit isn't so easy in a pileup accident resulting in a jumble of mangled vehicles.

"Individual companies will make their own decisions on whether they want to try to impose a surcharge or not, but given the publicity around this incident as well as the state police issuing a single accident report and not citing anybody, I think there will be a fair amount of understanding on the part of insurance companies," Mr. O'Brien said.

Any drivers involved in the pileup who are surcharged can appeal to the state Division of Insurance, which holds hearings in Worcester and several other cities around the state. The agency charges $50 to process an appeal, which can be submitted in writing or handled in a brief hearing.

A state Division of Insurance spokeswoman said the agency would take the state police accident report's findings into consideration in deciding any insurance surcharge appeals related to the Worcester crash.

In the event the division gets numerous surcharge appeal requests related to the I-290 pileup, the agency could conduct a "paper review" deciding the issue for all affected drivers rather than holding numerous separate hearings, she said.

"Even before it comes to an appeal, work with your agent. Work with your insurance company," Mr. O'Brien recommended. "Let them know all the facts and circumstances."

As for the weather conditions to be blamed in the state police accident report, the source of the slippery highway surface wasn't black ice, which forms from moisture in the air, but rather drizzle that fell as water and quickly froze to the roadway, said Glenn Field, the warning coordination meteorologist at the National Weather Service forecast office in Taunton.

The agency's forecasts had mentioned of the possibility of spotty freezing drizzle, Mr. Field said, but the prediction wasn't solid enough to warrant an advisory on Saturday. The forecast became more certain on Sunday morning, with a freezing drizzle advisory at 5:37 a.m. on Sunday.

"The problem is, who's going to be hearing it at 5:37? It doesn't make the TV broadcasts, but it just wasn't clear until that time," Mr. Field said.

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